1. Field of the Invention
The present invention relates to a rechargeable battery, and more particularly, to a method for breaking a current flowing through the rechargeable battery.
2. Description of the Related Art
A typical rechargeable battery includes a nickel-cadmium (Ni—Cd) battery, a nickel-metal hydride (Ni-MH) battery, a lithium (Li) battery and a lithium ion (Li-ion) rechargeable battery, etc. Especially, the lithium ion rechargeable battery has an operating voltage that is three times higher than that of the nickel-cadmium battery or the nickel-metal hydride battery that are commonly used as a power supply of the portable electronic devices. In addition, the lithium ion rechargeable battery has been widely used because it has higher energy density per unit weight.
The rechargeable battery uses lithium group oxides as cathode active material and carbonic material as anode active material. Generally, the rechargeable battery is divided into a liquid electrolyte battery and a polymer electrolyte battery, according to a kind of an electrolyte used in the rechargeable battery. The lithium ion rechargeable battery uses a liquid electrolyte, and the lithium polymer rechargeable battery uses a polymer electrolyte. The lithium ion rechargeable battery has been fabricated in various types such as a can type, a rectangular type, a pouch type, etc.
In addition, a protection circuit is attached to a bare cell lithium ion battery for performing basic charge/discharge functions. The protection circuit is packaged together with the battery to form a battery pack.
The protection circuit installed in the battery pack selects a charging path when the lithium ion battery is connected to a charger, and enables the lithium ion battery to be stably charged. On the other hand, when the lithium ion battery is connected to a portable electronic device, the protection circuit selects a discharging path and enables the battery to be stably discharged. Further, when the lithium ion battery is being charged or discharged, the protection circuit detects an over-current condition by monitoring (e.g., reading) a current value of the lithium ion battery, and breaks a current path of the lithium ion battery when the detected current value exceeds a value (e.g., a predetermined value).
However, the current breaking method has a problem that it is difficult to accurately calculate a current breaking timing according to a current value when the current value is continuously changing.
In addition, the lithium ion battery is gradually overheated when it is continuously being charged or discharged. However, the protection circuit breaks a current path only when the current exceeds a certain threshold value. Therefore, the protection circuit does not take into account the overheating time of the lithium ion battery to determine when to break a current path.